1. Field of the Invention
The present invention relates to a belt device and to an image forming apparatus such as a facsimile machine and a printer employing an electrophotographic recording method.
2. Description of Related Art
In a related-art image forming apparatus employing an electrophotographic recording method, a recording medium including a not yet fixed toner image formed thereon is inserted in a fixing device, so that the toner image is fixed on the recording medium with application of the heat and pressure. Such a related-art fixing device includes a pressurizing member and a fixing member including a cylindrical metallic core having a heat source disposed thereinside. The pressurizing member applies the pressure with respect to the fixing member through a belt member to form a nip portion through which the recording medium with the not yet fixed toner image is inserted.
Patent Document 1, for example, discloses a related-art fixing device including: a heating member, serving as a fixing member, rotatably driven; a belt member, disposed in contact with the heating member, forming a fixing region between the heating member and thereof; a pressurizing member, disposed opposite to the heating member, pressing the heating member with a prescribed pressure by way of the belt member; and a pressing member pushing the pressurizing member. The pressing member can evenly adjust a pressure distribution in the nip portion, thereby enhancing the quality of the image on the recording medium.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2005-189746
The related-art fixing device disclosed in Patent Document 1, however, can cause the belt member to be not stably driven. For example, since the pressurizing member pressing the fixing member with the prescribed pressure slides in contact with an inner circumferential surface of the belt member and presses the fixing member through the belt member, frictional resistance between the inner circumferential surface of the belt member and the pressurizing member is increased, causing an increase in a driving torque of the fixing member. Consequently, an abnormal noise can be generated from a drive motor of the fixing member, or the related-art fixing device can be poorly driven caused by synchronization loss of the drive motor. In addition to such drawbacks, the pressurizing member can easily deform in an arch shape with an increase in a frictional force between the pressurizing member and the belt member in the related-art fixing device. In a case where the pressurizing member is returned to an original state from the arch shape in excess of deforming limitation, a friction noise can be generated.
The present invention is proposed in consideration of the aforementioned situations, and provides a belt device capable of allowing a belt to be stably driven and an image forming apparatus including the belt device.